I've had a tooth break off of one and
junk a case out.
I've had the cone shear off of the gear on
the replacement upper from problem mentioned
previously.
I've had a couple of them simply just chunk out
the gear teeth.
I had 2 sets cyro treated at the same time,
one set still looks good, the other set started
to chunk out.
I've convinced myself the merc is having these
things made in China
So, no, you're not alone.